1. Field of the Invention
This invention relates to a regulatable field emitter device and, more particularly, relates to a field emitter device having control of the electron emission therefrom.
2. Description of the Related Art
Electron emission from field emitters has been difficult to control. If too much current is emitted from a field emitter, the field emitter may destroy itself due to excessive heat generation by current induced joule heating. Furthermore, heavily doped semiconductor field emitters or those having an elongated shape which permits avalanche breakdown are susceptible to destruction from too much electron emission due to heating, e.g. the conduction band of the semiconductor is populated with thermally generated carriers.
In the art of field emitters, the term "field emitter array (FEA)" structure is customarily used to generically refer to one or more field emitters, each of which has its own integral extractor gate and associated extraction aperture. Typically, a large number of field emitters are used in the art for tasks such as controlling the luminance on portions of a luminescent screen. Field emitters include metallic field emitters, thin-film field emitter cathodes and semiconductor cones. Known methods to limit the current output of a field emitter have been proposed. A sufficiently high resistance in series with the field emitter is known to restrict current emission from the field emitter. Greene and Gray in U.S. Pat. No. 4,513,308 proposed controlling field emission from a semiconductor device by back-biasing a PN junction. Furthermore, Gray et al. in "A Vacuum Field Effect Transistor Using Silicon Field Emitter Arrays" in the IEDM Technical Digest, Dec. 7-10, 1986, pp. 776-779 and in the proceedings of the Materials Research Society, Volume 76, 1987, p. 25, proposed control by velocity saturation inside the semiconductor field emitter of a vacuum field effect transistor. The vacuum field effect transistor proposed by Gray et al. in these publications uses electron emission from a field emitter, rather than a depletion region under a gate of a solid state field effect transistor, to control the switching of the vacuum field effect transistor. In this vacuum field effect transistor, the velocity saturation inside the field emitter acted to restrict current flow.